Targeting nanoplastic and microplastic removal in treated wastewater with a simple indicator

With growing concerns over plastic accumulation in the environment, it is imperative to quantify nanoplastic and microplastic release to water bodies via water treatment plant effluent streams. Current methodological limitations present a major challenge for continuous monitoring of nanosized pollutants in effluent streams. In this work, a novel correlation was established between removal of nanoplastics and total suspended solids (TSS) during aggregation-based wastewater treatment. The established correlation successfully predicted nanoplastic removal for a wide range of relevant nanoplastic properties, including polymer type, size, surface functionalization and ageing history, under 41 different physico-chemical and activated sludge treatment conditions (R2 = 0.92; n = 117). The results of our correlation reveal a predicted nanoplastic removal between 39% and 69% for typical water treatment effluent streams governed by current TSS regulations in North America. The study also reveals the potential of using TSS as a simple metric to estimate microfibre, microsphere and microfragment removal. Although it is widely acknowledged that nanoplastic and microplastic contaminants are omnipresent in the environment, the role of water treatment plants in the fate of these contaminants is unclear. Correlating nanoplastic removal with total suspended solids removal in water is shown to be a reliable method for predicting how much nanoplastic can be removed by wastewater treatment plants.